1. Field of the Invention
The present invention relates to a color cathode ray tube, and more particularly, to a tension mask frame assembly structure for a color cathode ray tube.
2. Discussion of the Related Art
FIG. 1 is a schematic sectional view of a general color cathode ray tube, and FIG. 2 is a sectional view of a panel of the color cathode ray tube of FIG. 1.
Referring to FIG. 1, the general color cathode ray tube is provided with a panel 1 that is a front glass, a funnel 2 that is a rear glass fastened to the panel 1, a fluorescent screen 4 formed on an inner surface of the panel 1, an electron gun that is the source of electron beams 6 irradiated onto the fluorescent screen 4, a mask 3 for guiding the electron beams to the fluorescent screen 4 corresponding to selected colors, and a main frame 7 for supporting the mask 3.
The color cathode ray tube is also provided with a spring 9 for fastening the mask-frame assembly to the panel, and an inner shield 11, fixed to the frame, for serving as a shield so that the cathode ray tube is little affected by an external earth magnetism during its operation. The color cathode ray tube is sealed in a high vacuum state.
The operation of the color cathode ray tube as constructed above will be explained.
The electron beams 6 radiated from an electron gun 13 mounted in a neck of the funnel 2 strike the fluorescent screen 4 formed on the inner surface of the panel according to an anode voltage applied to the cathode ray tube. At this time, the electron beams 5 are deflected in upward, downward, left, and right directions by a deflection yoke 5 before they reach the fluorescent screen to form a picture.
A two/four/six-electrode magnet 12 corrects the moving trace of the electron beams 6 so that the electron beams 6 accurately strike the predetermined fluorescent material, and thus the color purity is prevented from being inferior.
The cathode ray tube is in the high vacuum state, and thus may be easily cracked under an external impact. To prevent this, the panel 1 is designed to have a structural strength that can endure the atmospheric pressure. Also, by mounting a reinforcement band 14 on a skirt of the panel 1, the stress acting on the cathode ray tube of the high vacuum state is dispersed to secure its impact-resistant performance.
Conventionally, a spring holder 10 (See FIG. 4) is welded on the frame 7 of the mask assembly. One end portion of a spring 9 for enabling the spring holder 10 to fasten to the panel 1 is fixed to the spring holder 10 by welding, and the other end portion of the spring 9 forms a free end having a spring hole 9a formed thereon. The spring 9 has a bent portion to be properly spaced apart from the frame. Meanwhile, a fixing pin 15 is formed on the inner surface of the panel, and the mask-frame assembly is fixed to the panel by fastening the fixing pin 15 of the panel into the spring hole 9a. 
As described above, the mask-frame assembly is detachably fixed to the panel 1, and thus fluorescent stripes and black matrices can be formed on the inner surface of the panel by repeating the process of coating a photoresist material including a photosensitive material or fluorescent material slurry on the inner surface of the panel in a state that the mask-frame assembly is separated from the panel, and then exposing them to light in a state that the mask-frame assembly is fasten to the panel.
However, since the mask-frame assembly is assembled to the panel 1 by welding and using the spring pressure of the spring 9, the electron beam is not just landing on a specified position without any positional deviation, it deviates from its original position due to an impact by dropping and so on as shown in FIG. 3. That is, the position on which the electron beam strikes the fluorescent material deviates from its center, and this causes a color mismatch that is called a mislanding to occur, thereby deteriorating the picture quality. Conventionally, in order to minimize the color mismatch due to the impact, there have been measures for preventing the positional deviation of the mask-frame assembly such as shape improvement of the spring, reinforcement of the spring pressure, etc.
As the cathode ray tube is becoming large-sized, the weight of the mask-frame assembly is being increased, and thus it becomes necessary to reduce the weight of the panel and to place the mask-frame assembly closest to the inner surface of the panel. However, the shape improvement or the material for the spring is limited with the increase of the spatial limitation and manufacturing cost.
Meanwhile, Japanese Patent Unexamined Publication No. 10-125247 discloses a cathode ray tube in that a mask-frame assembly is assembled with a panel by fastening a fixing pin formed on an inner surface of the panel to a spring hole formed on one end portion of a spring of which the other end portion is fixed to the mask-frame assembly directly or through two or more junction points of a spring holder. In this cathode ray tube structure, it is prescribed that (A/B)xc3x97Wxe2x89xa65.0, where A(cm) is a distance between the center of the spring hole and the center of the junction point most adjacent to the spring hole (i.e., the shortest junction point), B(cm) is a distance between the center of the shortest junction point and the center of the junction point farthest apart from the spring hole (i.e., the farthest junction point), and W(kg) is a shared weight of the mask-frame assembly exerted on each spring for supporting the mask-frame assembly.
However, according to this cathode ray tube structure, the color mismatch due to the positional deviation still frequently occurs during the process of repeating insertion/separation of the spring onto/from the fixing pin of the panel, and the manufacturing cost is increased due to waste of unnecessary materials for the spring holder to secure the welded junction points. Also, the spring holder interferes with a damper wire installed on a sub frame of the mask-frame assembly for damping the vibration of the assembly.
Accordingly, the present invention is directed to a color cathode ray tube that substantially obviates one or more problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a color cathode ray tube that can optimize a distance between a spring hole of a spring and a welded junction point and a distance between the junction points with respect to the weight of a mask-frame assembly.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a color cathode ray tube includes a mask-frame assembly and a panel that are assembled together by fastening a fixing pin formed on an inner surface of the panel into a spring hole formed on one end portion of a spring of which the other end portion is fixed to the mask-frame assembly directly or through two or more junction points of a spring holder, wherein the cathode ray tube satisfies the condition of 5.0 less than (A/B)xc3x97Wxe2x89xa68.0, where A(cm) is a distance between a center of the spring hole and a center of the junction point most adjacent to the spring hole (i.e., the shortest junction point), B(cm) is a distance between the center of the shortest junction point and the center of the junction point apart farthest from the spring hole (i.e., the farthest junction point), and W(kg) is a shared weight of the mask-frame assembly exerting on each spring for supporting the mask-frame assembly.
Here, it is preferable that an elastic modulus of the spring is in the range of 18000xcx9c24000 kgf/mm2.
Also, it is preferable that a thickness of the spring is in the range of 1.0xcx9c1.5 mm.
According to the present invention as constructed above, the relative positional deviation between the mask-frame assembly and the panel is minimized, and thus the color mismatch (i.e., mislanding) is reduced during the operation of the cathode ray tube.
It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.